/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.objcoding.calcite.csv.translate;

import org.apache.calcite.adapter.enumerable.EnumerableConvention;
import org.apache.calcite.adapter.enumerable.EnumerableRel;
import org.apache.calcite.adapter.enumerable.EnumerableRelImplementor;
import org.apache.calcite.adapter.enumerable.PhysType;
import org.apache.calcite.adapter.enumerable.PhysTypeImpl;
import org.apache.calcite.linq4j.tree.Blocks;
import org.apache.calcite.linq4j.tree.Expressions;
import org.apache.calcite.linq4j.tree.Primitive;
import org.apache.calcite.plan.RelOptCluster;
import org.apache.calcite.plan.RelOptCost;
import org.apache.calcite.plan.RelOptPlanner;
import org.apache.calcite.plan.RelOptTable;
import org.apache.calcite.plan.RelTraitSet;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.RelWriter;
import org.apache.calcite.rel.core.TableScan;
import org.apache.calcite.rel.metadata.RelMetadataQuery;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rel.type.RelDataTypeFactory;
import org.apache.calcite.rel.type.RelDataTypeField;

import java.util.List;

/**
 * Relational expression representing a scan of a CSV file.
 *
 * <p>Like any table scan, it serves as a leaf node of a query tree.</p>
 */
public class CsvTableScan extends TableScan implements EnumerableRel {
    final CsvTranslatableTable csvTable;
    final int[] fields;

    protected CsvTableScan(RelOptCluster cluster, RelOptTable table,
                           CsvTranslatableTable csvTable, int[] fields) {
//    super(cluster, cluster.traitSetOf(EnumerableConvention.INSTANCE), ImmutableList.of(), table);
        super(cluster, cluster.traitSetOf(EnumerableConvention.INSTANCE), table);
        this.csvTable = csvTable;
        this.fields = fields;

        assert csvTable != null;
    }

    @Override
    public RelNode copy(RelTraitSet traitSet, List<RelNode> inputs) {
        assert inputs.isEmpty();
        return new CsvTableScan(getCluster(), table, csvTable, fields);
    }

    @Override
    public RelWriter explainTerms(RelWriter pw) {
        return super.explainTerms(pw)
            .item("fields", Primitive.asList(fields));
    }

    @Override
    public RelDataType deriveRowType() {
        final List<RelDataTypeField> fieldList = table.getRowType().getFieldList();
        final RelDataTypeFactory.Builder builder =
            getCluster().getTypeFactory().builder();
        for (int field : fields) {
            builder.add(fieldList.get(field));
        }
        return builder.build();
    }

    @Override
    public void register(RelOptPlanner planner) {
        planner.addRule(CsvRules.PROJECT_SCAN);
    }

    @Override
    public RelOptCost computeSelfCost(RelOptPlanner planner,
                                      RelMetadataQuery mq) {
        // Multiply the cost by a factor that makes a scan more attractive if it
        // has significantly fewer fields than the original scan.
        //
        // The "+ 2D" on top and bottom keeps the function fairly smooth.
        //
        // For example, if table has 3 fields, project has 1 field,
        // then factor = (1 + 2) / (3 + 2) = 0.6
        return super.computeSelfCost(planner, mq)
            .multiplyBy(((double) fields.length + 2D)
                / ((double) table.getRowType().getFieldCount() + 2D));
    }

    public Result implement(EnumerableRelImplementor implementor, Prefer pref) {
        PhysType physType =
            PhysTypeImpl.of(
                implementor.getTypeFactory(),
                getRowType(),
                pref.preferArray());

        return implementor.result(
            physType,
            Blocks.toBlock(
                Expressions.call(table.getExpression(CsvTranslatableTable.class),
                    "project", implementor.getRootExpression(),
                    Expressions.constant(fields))));
    }
}
